Means for tensioning rods and the like



Sept. 4, 1956 s. R. WOOLCOCK MEANS FOR TENSIONING RODS AND THE LIKE 5 Sheets-Sheet 1 Filed March 2,i 1954 6TA NLEY 'R/cHA R) 14 0mm '5 MW At tovx C Sept. 4, 1956 Filed March 2, 1954 S. R. WOOLCOCK MEANS FOR TENSIONING RODS AND THE LIKE 5 Sheets-Sheet 2 STANLEY RICHARD Waautoc Sept. 4, 1956 s. R. WOOLCOCK ,7

MEANS FOR TENSIONING RODS AND THE LIKE Filed March 2, 1954 5 Sheets-Sheets \Zww r mm m .5. I

STANLEY RICHARD wwLcock Attornej Sept. 4, 1956 s. R. WQOLCOCK 2,761,649

MEANS FOR TENSIONING RODS AND THE LIKE Filed March 2, 1954 5 Sheets-Sheet 4 SJ'ANLEY RIcH-ARD WdaLCaCK Sept. 4, 1956 s. R. wooLcocK 2,761,649

MEANS FOR TENSIONING RODS AND THE LIKE Filed March 2, 1954 5 Sheets-Sheet 5 STANLEY 'RJcHARD waoLcacg Att vufj MEANS non TENSIONING RODS AND THE LIKE Stanley Richard Woolcock, Southampton,

signor to J. J. Udalls Building Company, Limited, Southampton, England, a company of Great Britain Application March 2, 1954, Serial No. 413,668 Claims priority, application Great Britain March 3, 1953 7 Claims. (Cl. 254-29) England, as-

This invention relates to means for tensioning rods, wires and the like, hereinafter referred to as rods, the object being to provide improvements therein.

According to this invention apparatus for tensioning rods, as above defined, comprises a tension applying element, a tubular compression element, the tubular compression element being adapted to receive a rod which is to be tensioned and also adapted to be disposed between said tension applying element and an abutment on a structure containing said rod, a first gripping device adapted to be mounted on and secured to said rod disposed in said tubular compression member, elements mounted on said tension applying element and adapted to engage said first gripping device, and a second gripping device adapted to be secured to said rod in abutting relation to said abutment on the said structure.

The apparatus may comprise a fluid-operated jack, a

tubular compression element providing an extension of the ram of said jack and having slots in its wall, a first gripping device adapted to be mounted on and secured to a rod and also adapted, when secured to said rod, to be inserted into said tubular compression element, claw elements pivotally mounted on said jack and adapted to enter said slots in said tubular compression element whereby to engage said first gripping device, and a second gripping device adapted to be disposed on and secured to said rod. The apparatus may also comprise an abutment element, which may be a plate or a member having twowalls spaced apart, adapted to be disposed between and in abutting relation to said tubular compression element and a structure.

In this specification any reference to ends of a structure or formwork should be construed to include sides or other faces or parts of the structure or formwork between which rods, Wires and like members are disposed and are tensioned or are to be tensioned.

, In the accompanying drawings:

Fig. 1 is a diagrammatic plan view of one form of the invention adapted for post-tensioning reinforcing rods in a reinforced concrete structure.

Fig. 2 is a side elevation of Fig. 1.

Fig. 3 is a transverse section on line III-lII of Fig. 1.

Fig. 4 is an enlarged elevation of a detail.

Figs. 5 and 6 are transverse sectional elevations on lines VV and VI--VI, respectively, of Fig. 4.

Figs. 7 and 8 are enlarged fragmentary sectional elevations of details.

Fig. 9 is an elevation of a modified form of a detail of the apparatus.

Fig. 10 is a sectional side elevation, on line X-X of Fig. 11, of a modified form of apparatus for tensioning reinforcing rods, and

Fig. 12 is a fragmentary sectional elevation showing a modified arrangement of apparatus, and

Fig. 11 is a sectional plan view on line Xl-XI of Fig.

Fig. 13 is a transverse section on line XIII-XIII-of Fig. 12.

2,761,649 Patented Sept. 4,:1956

In Figs. 1 and 2, the concrete structure 11, which may be a beam, has been partially constructed, but a passage 12 has been left therein for the reception of reinforcing wires 13, 14. When these reinforcing wires have been tensioned, the passage 12 will be filled with cement grout-= anchorage plate and the face 19 of the concrete so as to take up any irregularities in the surface of said face. The thrust plate 18 has in it a large hole 20, whilst the anchorage plate 17 has an array of holes 21, one for each re-' inforcing wire 13, 14 which is to be provided in the structure. The reinforcing wires are threaded through the passage 12 in the concrete structure 11, through the hole 20 in the plate 18, and one wire through each hole 21 in the plate 17.

The reinforcing wire 13 is the one which is about to be tensioned, the other wires 14 being disposed loosely in position until it is required that they be tensioned, the array of holes 21 in the plate being arranged in the desired pattern or arrangement of the reinforcing wires in the structure.

A gripping device 22, hereinafter referred to as the anchorage grip, is disposed loosely on the wire 13 adjacent the outer face of the anchorage plate 17.

The anchorage grip 22 comprises (Fig. 7) an outer semi-circular in cross-section to form a tubular inner member and have a serrated inner surface 28 which provides, a serrated bore to said inner member. The wire 13 is threaded through the outer sleeve 25, and the two inserts 27 are then placed inside the sleeve so as to em brace the wire and, when the device is to be secured to the wire, are then driven into the sleeve so that the serrated inner surfaces 28 of the two inserts are forced into contact with the wire 13; thereby the complete grip 22 is attached to the Wire 13. p

- A spacer 23, provided by a tubular sleeve, is disposed loosely on the wire adjacent that end of the gripping device 22 which is remote from the plate 17. At some distance from the spacer 23, and nearer the end of the wire 2 13, a second gripping device 24, hereinafter referred to as the stressing grip, is disposed on the said wire in secure gripping engagement therewith.

The stressing grip 24 is of the form shown in Fig. 8, wherein two wedge shaped inserts 27, similar to those comprised in the grip 22, are disposed within a long steel sleeve 29 which has a bore 30 which is partially tapered at 31 at one end. A plug 32 is screwed into the wide end 33 of the bore of the sleeve 29, and a helicalcompression spring 34 is disposed in the portion 35 of the bore 30, which portion is cylindrical, and between and abutting the inner end of the plug 32 and the inner or wide end of the tapered tubular member formed by the two inserts 27. When the reinforcing wire 13 is threaded through the sleeve 29, the spring 34 and the plug 32,

and the two inserts 27 are placed in the sleeve and in embracing engagement with the wire, the action of screwing the plug 32 into the sleeve 29 will cause the spring to urge the inserts 27 tightly into the tapered bore portion SW13, are threadeclainto a steel tube 36. The steel tube 36 .is .formed as an extension of the .ram of a hydraulic jack 37, either as a fixed or removable extension of said ram.

flhvo "diametrically copposed :slots :38 (Figs. 1 Land 7) aresprovidedsin .thectube '36 near .tozitsrouterfendfiQ. The loose -a'nchorage1grip 22 and spacer 23ers eso :positi'oned onsthe wire 13sthat-Whenthetuheiis placed with its outer end 39 abuttingihe anch'orage:plate s17,asiin rFigs. land 7, :the ;grip '22- and spacer .23 are accessible '.through the slots :38.

{Two further diametrically opposed slots 40 .(Figs. 1 and 8y) -alsoiare disposed in the tubefifibetween the slots 38::and theebod-yof theijacki37. i'l'he stressing 'glip-i24 is so..po,sitioned on the wire .13 that when .the ctube :361is placed with its outersend 39 abutting themrichoragezplate 17,, es inhig. t1, (the :said grip :is-accessibleathrough the s1ots'n40, and the claws 4'1a0f :arms 42, hereinafter .described, --can ibepassed through the-said slots '40 .at .tpositions between \the:said:grip M ami the .outerend $39 .of the itube.

ll h'ev jack .37 comprises 'aipump 43 :having a handle 44 for manual actuation. Awharness 45 .is;providediwhich comprises a cross-head 46 for disposal laterallymcross and in [engagement with the base -47 ofthe :jack, :and two arms 42 which are each vpivotally connected by'one end to the cross-head :at 48 and which extendalong twO opposite sides of thejack, the other or free end of each :said arm'being provided with auclaw 41, the said two claws 'being passed through the slots 40in thezsteel tube 36 .for the purpose-described. Thetwo arms -42 form jawsyandta locking sleeve '49 is disposed oversaid jaws so that'when-thesleeve is pushedtowards the: claws 41 the two jaws-are closed towards ieach otherrso as'to retain both -claws projected through the slots -40 into the'interior'of the tube=36; conveniently,-.a suitable taper 50 .isgprovided on the outeredgesof thetwo -jaws so that wheuthe-lockingsleeve 49 isipushed along the jaws the 'twoclaws 41willclose .on .to .each 'other. .The two jaws are also shown dotted, .in anexaggerated :open position in-Fig. ltorclarity.

.A .liquid container -51 is mounted on the=crossl1ead 46 and'is suitably connected .to .the jack 37 .so that on operation of thepump .43the liquid is forced into the jackjsoas .toproject the tube36 therefrom. Agpressure gauge 52'is mounted on the crossheadlfor indicating-the hydraulic pressure-inthe jack. A-scale53 :is-mounted on thetube .36 .and covqperates with aniindicating mark 54 on'the' body of the jack so-as to indicate the extent of ,projeetion of the tube .from the jaek;-..the scalemay be attached to .theztube 36 in-the position indicated in Fig. "1, or .in any other suitable positiomlfor exarnple, between the jaws 41 andthe outersend 39 of the-tube was to avoid .fouling of .theconnection of-the scale'to the tube by the-jawswhen extension of theijackexceeds the distance between thejaws and the-body of thejack.

In use, the; jack 37. is suitably supported :in:a .-position, which may be horizontal so that .the axis of the ram :of the'jack and of the .tube 36iis substantially aligned with theaxis or the-hole '21 .in :the plate :17 through which the reinforcing wire-13 passes. Thetouteriend of-rsaid wire'1'3, together with the.anchorage ,grip-.22,-.spacer -23 and stressing .grip 24 are inserted intothestube 36, the jaws comprised ,by the.arms-42-and claws 41--are.closed upon the tube 36.50 that-the said claws enter..the-s1ots-40 atpos'itions between thegrip 24 and the outertend 3-9 of 'the'tube, the locking sleeve 49-is,pushed-over the outer ends of the arms 42 :so as to-retain thet-clawsiin positiontinthe tube slots, and 'the-saidx-outer end .39 of the tube 36 is placed'in -abutmentawiththeouten-faee ofathe plate 117.

'The pump-handle 44 is operated ct-oicauserliquidtto enter the jack r37, whereupon the ram-tof zthe jack is'rprojeeted from the jack, z-together with"the' 'tube's3'6. Thereupon, the tube 36 operates asta compression -element to 4 force the jack 37 and the concrete structure 11 apart. As the .jack .moves away from the .structure 11, the.claws 41 engage the end of the stressing grip 24 which is nearer the structure 11 and apply tension to the wire 13. The end of the wire 13 which is remote from the jack 37 is anchored in any suitable.manner.to the end of the structure 11 which also is remote from the jack; for example, anchorage and packing ,plates may be :disposed at said other end of structure 11, the wires are passed through holes insaid plates, and anchorage grips, similar to the grips Z2, are'secured'to each wire-outwardlyof'the anchorage plates. The anchorage grip 22 and spacer 23 are .retained adjacent the plate 17 .during tensioning of the wire 13 by a locating key 55 which is passed into aslot38 so'asto abutthe ends "ofthe-slot '-38"a1rdspacer 23 remote from the;plate:17. When the zappropriate tension has been applied to the wire 13, which can be determined by reading the gauge 52 and/or the scale 53, thelocatingkey' '55 is replacedrbyra wedge, drift 'or other tool whiclris driven:so:as-to.'drive the spacer l23 against the inserts 27 of the=grip 22 and force said inserts '--into the :sleeve .25, and the whole grip 22 is ldriven tightly up to :the outer .face 'of the plate .17, the inserts 27 bein'g locked tightly onztorthe 'wire .13 by the tension in .said wire. .Thereupon, the-hydraulic pressure in:the jae'k 871is released, for :example, byopening a valve:56, and -the tension .applied :to .the wire :13 is transferred from the jack to the anchorage grip.22. The jaws' of :the jaek are opened, upon withdrawal of :the sleevei49, and the jartk together with'tlte.tube:36-are withdrawn from the wire 13. .The wireisthen severed,:between the grip 22' and spacer 23, and :the spacer :23 :and -:grip 24 are f recovered, the grip.22 beingl-lefti in position and,"in some 'cascs, sub- *sequently being encased .in concretefilling in the =-end-recess .16 of the concrete structure 11.

:Each of the other reinforcing -wires 14 are similarly tensioned. .The. endi39-ofithesteel'tube 36 is'fluted longitudinally-on its outer :surface at 57, Fig. 3, 'to enable-iit to be i placed between adjacent reinforcing *wires' whilSt tension is 1 being-applied to one wire.

When all o'fthe reinforcing wires, or all those wires which-are to be tensioned, have been tensioned concrete grouting may be poured: into"the:passage 12 in theistructure =11, through. a.'duct:58, and 'allowedrto set-or harden.

.lnthe eventcoftheends of (the concrete structure being disposed in :awkward positions, whereit is .not possible to accommodate Lthe jack 'zincaxial :alignrnent'with the holes .in the anchoragexplates through which the rein- 'forcing wires pass, the steel tube 36 mayibebent-suitably longitudinally, or za. suitablyzbent tubular adaptor may he disposed between the tubex36 and the 'anchorage plate 17, to'enablethe ja'ckto be fplacediirna suitable operating position. Eor-example, ras illustrated in Fig. 1-9, fa -curve'd tubular adaptor 70, having:one end ishape'd or adapted similar to the end of thetubes36=with 'orificesl38 a'n'd flutes 57, .is (disposed between-the plate 17 :and the tube 36, being connected tozthe tubelafirby a sleeve or collar 71 which may be secured tO'ISald'tHhE'IOI adaptor. 'l'h'ereby, the jack may be inclined to thei'structure at arr-angle,

for example,.of 45 degrees.

The apparatus may be .used for applying pretension to the reinforcing wires. .:E0r::example,;-in "theiconstruction illustrated in Fi"gs..10and :Ll, :a substantially rectangular: box-like membervfifliisrprovided. Thezbox-eomprises two opposed end walls 61, 62 which ib'oth are orifice'd at63 .and 64, -irespectively, to allow Freinforcing wires 13 to be threaded therethrough. The'lboxifisrmade of steel .and the end'wa1l1621is :considerably ihicker than the--wall-. 61. The-top :ofvthe box is open,.="and azbottorn closing wall 65 is provided, whilst theeotherxtwo walls 66, L67 -which 3126643111631 are .of :sufiicient' thickness to resist endwise compression and so prevent the two end wallsatil and- 62 being pressed towards "each other. :The walls 66 and 67 maybe ribbedl'or otherwise-reinforced to inerease the-"said'compression strength.

In use, the box 60 is placed in position at one end of the shuttering or other formwork 59 for a concrete beam which is to be constructed, with the thinner end wall 61 abutting said end of the formwork. A thrust or packing plate 18 is placed between the .wall 61 and the end of the formwork so as to take up any irregularities in the end surface of the formwork. The reinforcing wires 13 are laid in the required positions in the formwork and one end of each wire is threaded through a hole 63 in the wall 61, then passed across the interior of the box and threaded through a hole 64 in the thicker wall 62, whereupon the gripping devices 22 and 24 and spacer 23 are applied to the end of the wire outside of the thicker end plate 62. The jack 37 and tube 36 are then applied in the manner described, with the end 39 of the tube abutting the outer face of the wall 62.

The end walls 61 and 62 of the box 60 are provided with a suitable array of holes so that suitable ones may be selected to suit the arrangement of reinforcing wires in the beam; or the Walls may be specially orificed to suit the beam which is being constructed.

After the tension of all reinforcing wires has, been taken by the anchoring grips 22 on said wires, the said grips being disposed tight up against the outer face of the wall 62 of the box 60, concrete is poured into the formwork 59 and allowed to set or harden.

Whilst setting is taking place the jack may be used on other beams, but the box 60 will have to remain in position until the required degree of setting of the concrete is achieved. When the concrete has set sufiiciently to hold the reinforcing wires 13 in contact therewith without releasing the tension therefrom, the portions of the wires which are disposed between the end walls 61 and 62 of the box are severed, whereupon the tension in the wires is transferred from the anchor grips 22 to the concrete.

Preferably, the wires are severed by applying an oxyacetylene or other cutting flame thereto; the action of the heat necessary to gradually burn through the steel of the wire is suflicient to release the stress on the wire in a manner which will not apply appreciable shock to the concrete, or at least suflicient shock as would rupture the bond between the concrete and the stressed wire.

By inclining the two end walls 61 and 62 in relation to each other, the reinforcing wires may be flexed slightly after leaving the end of the formwork 59, if it is desired to do this in order to splay the wires apart sufiiciently to allow the steel tube 36 to be disposed between adjacent wires, whilst applying the tension to the wires substantially perpendicularly to the outer thicker end wall 62.

The apparatus described may be applied to the construction of any pre-stressed concrete structure; for example, it may be applied to the construction of a beam which has anchor units incorporated in it at each end, together with preformed concrete or other moulding units disposed between and in abutment with said anchor units,

in which case the pre-tensioned wires may be severed as soon as concrete in the anchor units has been bonded to the wires, the main body of the concrete of the beam being filled into the moulding units afterwards so that said concrete is inert.

The apparatus may also be applied to the tensioning of rods, wires and like members in any other form of structure.

In the event of additional tension being required in the wire, for example, due to loss of tension when the gripping device 22 takes the load from the jack and the inserts 27 are drawn into the sleeve 25 by the wire, the wire is again tensioned with the grip 22-secure thereon, and a suitable shim, spacer or the like is placed between the said grip and the plate 17. This may be achieved by making the end 39 of the tube 36 U-shaped in section, or by disposing an adaptor so shaped, so as to provide an open side through which the shim or spacer may be passed. For example, an adaptor 73, Figs. 12 and 13, is disposed between the plate 17 and the tube end 39. The adaptor is U-shaped in section and is assembled with an open side 74 on top, or otherwise suitably, so that a shim or spacer 75 may be placed around the wire 13 and between the plate 17 and the grip 22 when additional tension has been applied to the Wire, for example, by reattaching the ram thereto before the wire is severed.

What I claim and desire to secure by Letters Patent is:

1. Apparatus for individually tensioning each of a plurality of rods comprising a tension applying element, a compression element adapted to be disposed between and in abutting relation with said tension applying element and an abutment on a structure containing said rod, and a first gripping device adapted to be mounted on and secured to said rod and to be connected to said tension applying element, said compression element being tubular and being open at that end adjacent said structure whereby said first gripping device and the portion of said rod on which said device is mounted may project from said structure and pass into and be disposed within said compression element, said tubular compression element being provided in its Walls with first longitudinal slots, and said tension applying element being provided with connecting elements adapted to project through said longitudinal slots in the compression element whereby to be connected to said first gripping device and to enable said rod to be drawn longitudinally within said compression element upon tension being applied to said rod by said tension applying element.

2. Apparatus according to claim 1 wherein said tension applying element is a fluid-operated jack, and each said connecting element is pivotally mounted by one end on said jack and has a claw on its other end, said claw being adapted to project through a said slot in said tubular compression member and to engage said first gripping device.

3. Apparatus according to claim 1 further characterized in that said tubular compression element is provided in its walls with second longitudinal slots whereby to allow access to a second gripping device which is mounted on said rod and disposed within said tubular compression member between said first gripping device and said abutment on said structure so that said second gripping device may be moved along said rod into abutting relation with said abutment and into gripping engagement with said rod to retain tension which has been applied to said rod.

4. Apparatus according to claim 1, further comprising an abutment element for disposition between and in abutting relation to said tubular compression element and a structure.

5. Apparatus according to claim 4, wherein said abutment element is an orificed plate.

6. Apparatus according to claim 4, wherein said abutment element is a member having two walls spaced apart and orificed.

7. Apparatus according to claim 1, wherein said tubular compression element is curved longitudinally.

References Cited in the file of this patent UNITED STATES PATENTS 

